Invasive Mussels Another Suspect in Resurgence of Algal Blooms

Invasive zebra and quagga mussels, introduced into the Great Lakes in the late 1980s, may also be contributing to the growing algal blooms in Lake Erie, though researchers disagree on their exact role.

The Great Lakes system as a whole has dramatically changed in the last 15 years because of zebra and quagga mussels,” said Andy Buchsbaum, regional executive director of the National Wildlife Federation’s Great Lakes Regional Center in Ann Arbor, Mich. “It used to be that it took three months for native mussels to filter all the water in Lake Erie. Now it takes three days. When you’re dealing with that dramatic a change to an ecosystem, then all the other stresses we’re talking about then exacerbate that.”

Because the mussels are filter feeders, they improve the clarity of the water. This can lead to more growth of algae and other aquatic plants on the bottom of lakes because it allows sunlight to reach deeper. The mussels could also be changing how phosphorus cycles through the lakes.

“The modeling would suggest that they don’t play that much of a role in controlling the total quantity of phosphorous, but they may affect the form of phosphorus by trapping particulate matter and then rejecting or excreting a more soluble form,” said Peter Richards, a senior researcher at Heidelberg University’s National Center for Water Quality Research in Tiffin, Ohio. “They may also shift the timing of when the phosphorus impacts the ecosystem somewhat, but it doesn’t look like they are a major factor in controlling total quantities.”

Researchers at Heidelberg University in Ohio say that the mussels likely play a larger role in near-shore environments, but not in the off-shore algal blooms.